Holley Carb or not???

[Clint44]

Our 2006 trike has a Demon carb which doesn't impress me at all. For performance,I think a Holley 4777 650cfm double pumper would work well. However,it's a proven fact that Quadrajets can be made to work extremely well,too. The big advantage of using one,IMO,is the smaller diameter primary throttle bores that allow better fuel mileage at cruise rpm and better low-speed throttle response. As mentioned before,they like lower fuel pressures than a comparable Holley because their float cavity is smaller.
Carb Mike,what mods (if any) do you make to the secondaries? Lighter spring or heavier?

[Geezer]

The Q-Jet was designed by the Rochester Div of GM.

They pulled out all the stops in carb design at that time, because
of the lurking EPA shit that started in the 70's, before FI came out.

All the stops, means they designed the Q-Jet to be one of the best
metering carbs ever made. Which it is .........

However in the early days, most hot-rodders did not understand the
complication of the Q-Jet, vs the more simple Holly design, which
became a favorite. Hence the reason that the Q-Jet got the bad
press of being "Quadra-Junk or Quadra -Crap".

Carb Mike took it upon himself several years ago to learn about the
Q-Jet and received his "PHD" in knowledge, which lead to his
sucess in making them work like they do.

As FI came on board, Rochester Division of GM sold the rights to
manufacture the Q-Jet to Weber. I believe the Carter Design AFB
was also sold to Weber, that is what the V8-Choppers use.

Edelbrock sold both of these, with their name, until sales went into
the trash can several years ago, at which time they quit selling the
Q-Jet design, but still sell the Carter - AFB design.

That is the reason BH went to the Demon Carb, which is owned by
Berry Grant.

The Demon is a very good carb, but they did have a few small quality
problems at one time. The Demon is basically a jazzed up verson of
the Holly design, that flows better due to body design. A 650cfm
Speed Demon will flow about 750-780 cfm, but all the crisp throttle
response of a small ventura carb.

Carb tuning many think is a "Black Science", but once you understand
them , all the dots fall into line. Especially with the tuning tools
currently available like the Wide Band o2 sensor set ups.

Reading plugs accuratly is just about impossible with the new gasoline we are using.

Remember all carbs no matter who makes them, will come rich from
the factory for liability reasons. Fat is happy - Lean is mean. Too
lean will hurt ya......

[gaston 2005 502]

Loaf and Bob,,

thanks for the updates of when where and why. i guess it is just like ford vs chevy, bad things are intensified and good things receive not much attention. i personally can work on a Q-jet, but i do not know shiiiite about a holley, so for me, i stick with a q-jet. Ford diesel trucks and chevrolet motors,, but i have not had any experience with after market motors,,,, yet. maybe someday when i am ready,,, dart or donovan

Darryl

[carburetormike]

Hi Clint, You asked "Carb Mike,what mods (if any) do you make to the secondaries? Lighter spring or heavier?"

On the #1901's The Air Valves are notched to bring in the Secondary Accel shot quicker, The undersides along with the bottom edges are roughed up to create more turbulence for better fuel atomization. On the #1910's I don't touch them. On both the Bypass holes are drilled into the Secondary accel shot pick-up tubes to more smoothly transition over to the Richer running "CE" Secondary Rods. The Secondary Rod height is set at 22/32" @ 71 degrees of Air Valve opening. The bottom throttle plate shaft is adjusted to open to 108 degrees, This helps to balance the air flow from the carb. so the front two cylinders don't run lean. And the Air Valve wind-up spring is set at 7/8 turn. Stock is 1 full turn. But the biggest improvement comes from the Choke Pull-off modification. In the past, I've seen opening times as slow as 4 seconds on some carbs. On average it's 2-3 seconds. I just simply drill the orifice to .013" and the timing moves up to 1-1:25 seconds, This brings in the Secondaries just as fast as a Boss Hoss can handle it. Any faster and the carb will bog.

Above is just one circuit of the five Incorporated into a Q-Jet. And each has has it's own list.

If I would ever sit down and write everything down involved with what a Stage 2 really is, I'd be giving away all my little secrets, So I may as well keep them under my hat and just rebuild them. Or maybe write a How to Rebuild and Modify an Edelbrock Carburetor Book and sell my secrets.

The only trouble is, I've become even more meticulous in making everything work like a Swiss Watch that I'm adding hours on top of the 10hrs it used to take for a rebuild. But the end product is what GM was shooting for in the first place.

http://videos.streetfire.net/video/1901 ... 683692.htm

So Geezer Should I change my screen name to Doctor Carburetor Mike ! ! ? ? Hee Hee

Respectfully Yours, Michael A. Levesque
AKA " Doctor Carburetor Mike " LOL
President Boss Hoss Riders Association carburetor.mike@netzero.com

[tjy]

Our 2006 trike has a Demon carb which doesn't impress me at all. For performance,I think a Holley 4777 650cfm double pumper would work well. However,it's a proven fact that Quadrajets can be made to work extremely well,too. The big advantage of using one,IMO,is the smaller diameter primary throttle bores that allow better fuel mileage at cruise rpm and better low-speed throttle response. As mentioned before,they like lower fuel pressures than a comparable Holley because their float cavity is smaller.
Carb Mike,what mods (if any) do you make to the secondaries? Lighter spring or heavier?

Clint, I'm by no means a carb/performace guy but the first thing i would do is; put on a good set of headers..I favor sanderson
JP-1 (jack phillips) model $600.00 usd and then I had Bob at mountain bh go thru and tune it ( the demon) My butt dyno really
noticed the difference.

tom